The neurocircuitry involved in hypothalamic hyperphagia and obesity will be investigated. Previous work has indicated the rostral terminus of this circuitry to be the paraventricular nucleus area. We plan to investigate the caudal projections, specifically the vagal complex, and the specific branches of the subdiaphragmatic vagus. The ontogeny of hypothalamic hyperphagia and obesity will also be explored. Previous findings indicate weanling rats with knife cuts will not become obese on a high-fat diet until 50 days old. However, knife cut weanling rats on a high carbohydrate diet become obese immediately. This research will be expanded using numerous diets and several biochemical assays to determine why weanlings are opposite adults.